The invention relates generally to a method of rapid prototyping and manufacturing and, more particularly, to laser sintering.
Rapid prototyping and manufacturing (RP&M) is the name given to a field of technologies that can be used to form three-dimensional objects rapidly and automatically from computer data representing the objects. In general, rapid prototyping and manufacturing techniques build three-dimensional objects, layer-by-layer, from a working medium utilizing sliced data sets representing cross-sections of the object to be formed. Typically an object representation is initially provided by a Computer Aided Design (CAD) system. RP&M techniques are sometimes referred to as solid imaging and include stereolithography, ink jet printing as applied to solid imaging, and laser sintering.
A laser sintering apparatus dispenses a thin layer of heat-fusible powder, often a fusible polymer powder, polymer coated metal, or ceramic, over a bed of the powder commonly referred to as the “part cake.” The laser sintering apparatus then applies thermal energy to melt those portions of the powder layer corresponding to a cross-section of the article being built in that powder layer. Lasers typically supply the thermal energy through modulation and precise directional control to a targeted area of the powder layer. Conventional selective laser sintering systems, such as the Vanguard system available from 3D Systems, Inc., use carbon dioxide lasers and position the laser beam by way of galvanometer-driven mirrors that deflect the laser beam.
The part cake typically includes a moveable build platform upon which the bed of powder is disposed. After a powder layer is fused, the build platform moves downward by an incremental distance and the apparatus then dispenses an additional layer of powder onto the previously fused layer and repeats the process of melting and selective fusing of the powder in this next layer, with fused portions of later layers fusing to fused portions of previous layers as appropriate for the article, until the article is complete. These articles are sometimes referred to as “built parts.” Each additional layer of powder is typically dispensed from a powder feed system that dispenses a measured amount of powder onto the part cake. A powder spreader, such as a blade or roller then picks up and spreads the powder over the part cake bed in a uniform manner.
Detailed descriptions of laser sintering technology may be found in U.S. Pat. Nos. 4,863,538; 5,132,143; and 4,944,817, all assigned to Board of Regents, The University of Texas System, and in U.S. Pat. No. 4,247,508 to Housholder.
Generally, once the part is built it remains within the process chamber under an inert atmosphere until the newly formed part has cooled. Cooling may require several hours or days. As a result, the RP&M apparatus may be inactive during the cooling time, which may cause the apparatus to be unavailable for subsequent builds.
RP&M apparatuses have been developed that include a removable build chamber in which the build platform may be disposed. The build chamber including the newly built part may be separated from the process chamber and the part can then be cooled in the build chamber. A fresh build chamber can then be placed into the process chamber so that a new part may be built. The build chamber must be positioned within the process chamber so that the powder bed and the build platform are properly aligned. Incorrect alignment of the powder spreader and the vertical travel of the build platform may result in the depositing of non-uniform powder layers and/or lateral misalignment on successive fused layers of powder. Building a part on an incorrectly aligned build platform may result in a defective part that may be unusable. Proper alignment of the build platform with the powder spreader may require a user to make many adjustments and measurements. The alignment process may result in loss time and inefficiencies in the RP&M process.
U.S. Pat. No. 6,554,600 describes a RP&M apparatus having a container that is manually inserted into the RP&M apparatus by physically lifting it up and placing it into the interior of the apparatus. Once placed in the apparatus, the container is stationary until it is removed from the container. The container is supported by rails on opposing sidewalls that position the container and align it with a reciprocatable overhead hopper system having a blade attached to the bottom of the hopper opening to deliver and then spread the powder. The insertable container has four side walls and a moveable platform having a size that is equal to the internal cross-section of the apparatus. A lifting mechanism moves the platform up and down as needed. After a part has been built, a user must physically lift the container including the part and any unsintered powder out of the apparatus. Physically lifting the container may be undesirable because the container may be heavy and the lifting process could cause the part to shift resulting in damage to the part.
Thus, there exists a need for a RP&M apparatus having a removable build chamber that can be quickly attached and aligned with a process chamber.